WO 09847751 A1 describes a pneumatic vehicle brake system, which is provided with a compressor, at least one air-consuming circuit, such as a service brake circuit, a parking brake circuit, a low-pressure auxiliary circuit and a high-pressure circuit, wherein the circuits contain compressed air tanks and demand valves. A first electrically actuatable valve, which is closed in home position, is disposed between the compressor and each consuming circuit. A second electrically actuatable valve, which is open in home position, is disposed between the compressor and the auxiliary circuit. The valves are actuated by an electronic control unit. The output ports of the first valves of the air-consuming circuits are in communication via check valves with the output port of the second normally open valve. Should a pressure demand be present in one of the circuits, for example because of insufficient tank pressure, the corresponding valve is opened by the control unit and, simultaneously, the second valve of the auxiliary circuit is closed. Failure of the compressor leads to a pressure drop, which is recognized by the control unit, which closes the valves or keeps them closed, thus maintaining the pressure in the circuits. A pressure regulating valve determines the pressure level. In the event of failure of the pressure regulating valve, overpressure is discharged via an overpressure valve. Pressure sensors monitor the circuits. The circuits are supplied with air via the second normally open valve and via the check valves connected upstream from the circuits. If the electrical system fails, all valves switch to home position. Nevertheless, the compressor continues to run and to supply the circuits with air via the second normally open valve of the auxiliary circuit, in which case the system pressure is determined by a low-pressure discharge valve of the auxiliary circuit. If a valve fails, the associated circuit can be supplied with air via the valve of the auxiliary circuit and the check valve. The known system is complex, since each consuming circuit is equipped with a compressed air tank.
DE 10004091 C2 describes a compressed air supply device for vehicle compressed air systems having a multi-circuit protective valve, a pressure regulator, a supply line for supplying the circuits of the multi-circuit protective valve with compressed air, and a compressor, which can be switched by means of a pneumatic switching mechanism, a pilot valve being provided to control the pressure regulator and the switching mechanism and a throttle being provided between the pilot valve and the switching mechanism. Each circuit contains a compressed air tank. The pilot valve is controlled and/or regulated by an electronic control and/or regulating unit. Pressure sensors monitor the pressure in the circuits and in the supply line.
The known air supply systems have the disadvantage that either they must be adjusted mechanically by the manufacturer or they must be parameterized by software.